The present invention relates to a device for moistening the inlet air or internal combustion engines having turbo-superchargers.
It is known to moisten the inlet air of Diesel engines provided with turbo-superchargers in order to reduce the Nox content of the exhaust gas. Such a method with corresponding device is described in WO 95/23286. In this known device a moistening means is traversed by the inlet air and water, wherein the inlet air, prior to its moistening, is compressed by the compressor of the turbo-supercharger and the energy inherent in the cooling water of the exhaust gases of the internal combustion engine is used for preheating the water before the same is introduced into the moistening means. Accordingly, in this case compressed air is moistened.
It is the object of the invention to provide a device for moistening the inlet air of an internal combustion engine with a turbo-supercharger with which the Nox reduction in the exhaust gas of the internal combustion engine is achieved in an especially simple manner at especially low cost.
This object is achieved by a device for moistening the inlet air of an internal combustion engines having a turbo-supercharger and which comprises:
a moistening means through which the inlet air and the moistening liquid flow and contact one another and which is disposed upstream of the compressor of the turbo-supercharger in a flow direction of the inlet air; and
an air/air heat exchanger disposed upstream of the moistening means in the flow direction of the inlet air, serving for preheating the inlet air and traversed by the atmospheric inlet air and the moistened and compressed inlet air of the compressor.
Accordingly, with the inventive solution the inlet air is moistened in a non-compressed condition. In order to enable such a moistening, the inlet air is preheated prior to passing the moistening means for which the compressed inlet air leaving the compressor of the turbo-supercharger and already moistened by the moistening means is used. The preheating is realized by means of an air/air heat exchanger traversed by the compressed inlet air. The compressed inlet air, heated not only by the realized preheating but also by the compression in the compressor, transfers a part of its thermal energy to the atmospheric inlet air in the air/air heat exchanger and is thus cooled. Accordingly, cooled and compressed air is introduced into the internal combustion engine.
The invention is particularly directed to Diesel engines or gas engines which, however, does not exclude that it can be used with other engines also.
The moistening of the inlet air in the moistening means is carried out adiabaticly.
The air/air heat exchanger can be a known intercooler with aircooling already existing with internal combustion engines.
For example, the air in the compressor of the turbo-charger is heated to a temperature in a range of 150-200xc2x0 C. by the carried out compression process. In the preheating step the atmospheric inlet air is heated by the heated compressed air to a temperature range of 35-120xc2x0 C. Simultaneously the heated compressed air is cooled from 150-200xc2x0 C. to about 90-100xc2x0 C. The corresponding moistening is carried out according to the invention without heating of the moistening medium (water).
According to a further development of the invention another moistening means is disposed upstream of the air/air heat exchanger in the flow direction of the inlet air, a heating device for the inlet air being disposed upstream of this moistening means. Accordingly, with this embodiment a first preheating of the inlet air by means of the above-mentioned heating device takes place which is followed by a moistening of the inlet air. Thereafter, the inlet air is again heated (second preheating) through the air/air heat exchanger by means of the compressed inlet air whereafter the inlet air is again moistened. Both moistening means are adiabatic moistening means.
Preferably, the heating device for the inlet air is an air/water heat exchanger for transferring the thermal energy of the cooling water of the internal combustion engine to the inlet air. The air/water heat exchanger can be traversed directly by the cooling water or an additional water circuit can be disposed therebetween.
According to an alternative embodiment the heating device is formed by an air/air heat exchanger serving for the transfer of the thermal energy of the exhaust gas of the combustion engine to the inlet air. Of course, with this embodiment a water circuit can also be interposed.
The compressed, moistened air leaving the air/air heat exchanger can be further especially cooled and/or once again moistened. Normally, a cooling is desired since the compressed air leaving the air/air heat exchanger is still too hot. So, an embodiment of the invention provides that a cooling device is interposed in the flow path of the compressed and moistened inlet air between the air/air heat exchanger and the combustion engine. For this, a normal intercooler, can be used.
Accordingly to another alternative a third moistening means is disposed in the flow path of the compressed and moistened inlet air between the air/air heat exchanger and the internal combustion engine. By this, an additional moistening and cooling of the inlet air is achieved. Preferably, the third moistening means is associated with a heat exchanger for heating the moistening medium (water). This embodiment corresponds to the embodiment described in WO 95/23286 according to which the moistening means flown through by compressed air is applied with heated water for the moistening and the heating of the water is carried out by means of a water/water heat exchanger of water/air heat exchanger which is traversed either by the cooling water or by the exhaust gas of the internal combustion engine.
Normally, an air filter is disposed upstream of the air/air heat exchanger in the flow path of the inlet air. However, for relieving the air filter the same can be disposed downstream of the moistening means in the flow path of the inlet air. With this embodiment a part of the impurities is already discharged through the moistening means.
The device according to the invention is especially used with Diesel engines of ships, boats and other vehicles. The Diesel engines of such vehicles frequently have a sea water circuit (salt water circuit) the water of which is either used itself for the cooling of the Diesel engine or serves for cooling the cooling water through a heat exchanger is the fresh water cooling. If such a sea water circuit is existing the moistening means is (are) appropriately applied with salt water either so that no special fresh water source is necessary. The salt water can be intercepted and recirculated to the conduit leading to the moistening means.
Of course, this does not exclude that river water or tap-water can be used instead of salt water.
The above-mentioned cooling device is appropriately controlled in response to the pressure of the turbo-supercharger in order to avoid condensation.